This invention relates generally to exercise machines in which a user operates a weight stack by means of a cable that is trained by means of a system of sheaves to an input mechanism via which the user imparts motion to the weight stack.
Principles of the present invention are embodied in an exercise machine for performing supination and pronation exercises. These exercises are for strengthening principally the forearm and biceps and comprise a twisting motion that takes place generally about the elbow. Supination comprises a clockwise twisting of the right forearm, typically from a palm down position to a palm up position, and a counterclockwise twisting of the left forearm, also from palm down to palm up. Pronation involves counterclockwise twisting of the right forearm and clockwise twisting of the left forearm, both from a palm up position to a palm down position. The typical person can execute approximately 180.degree. of supination and approximately 165.degree. of pronation.
The present invention comprises a new and unique machine organization for enabling the user to perform both supination and pronation exercises of both arms. Moreover, the machine of the present invention is conveniently adjustable to accommodate different users. Since the machine involves the user operating a weight stack via a cable, the weight against which the user exercises can be conveniently controlled by adding or subtracting weights to and from the stack.
Although the illustrated machine is for the particular exercise purposes of supination and pronation, the machine contains generic principles that can be embodied in other types of exercise machines. This is because the machine comprises what is referred to as "bi-cam". The bi-cam is a rotary cam having two 180.degree. segments. One of these segments is interactive with the cable during supination exercises. The other segment is interactive with the cable during pronations exercises.
The illustrated embodiment of the machine contemplates the user exercising only one arm at a time. The bi-cam, in combination with the weight stack, serves to adapt the resistance encountered during supination and pronation reasonably closely to the user's physiological ability, i.e. his or her strength curve. During an initial portion of both a supination and a pronation, the user can exert a greater torque than toward the conclusion of the exercise. The bi-cam takes this into account by automatically adapting the amount of cable that is displaced for a given amount of rotation of the bi-cam. In other words during an initial portion of both a supination and pronation, the cable is displaced a greater amount than it is toward the conclusion of the supination or pronation. Hence, even though the weight stack remains constant during an exercise, the effective torque which it imposes on the user is made variable in accordance with the general physiological capabilities of a person being able to exert a greater torque at the beginning of a supination or pronation than toward the conclusion of a supination or pronation.
The generic aspect of using the bi-cam to correlate the effective loading imposed on a user by a constant weight stack is applicable to other similar types of machines even though these other types of machines are not necessarily for performing just supination and pronation exercises.
Although the bi-cam comprises two 180.degree. segments that correlate generally with the 180.degree. of twisting that can be imparted during supination and pronation exercises, it is possible to adapt the bi-cam to other types of exercises which physiologically may not involve 180.degree. motion in opposite directions. By configuring the input mechanism between the user and the bi-cam in any of various ways, different ratios may be evolved for adapting the bi-cam to a particular exercise. For example, a gear mechanism which sets an appropriate gear ratio between the user input and the bi-cam is one way in which adaptation can be made.
The foregoing features, advantages, and benefits of the invention, along with the additional ones, will be seen in the ensuing description and claims which should be considered in conjunction with the accompanying drawings. The drawings disclose a preferred embodiment of the invention in accordance with the best mode contemplated at the present time in carrying out the invention which happens to be in a supinator/pronator exercise machine.